544 REPORT OF NATIONAL MUSEUM, 1898. 



downward. The epipterygoid rises at the basipterygoid and rests on 

 the anterior border of the petrosal and the posterior border of the well- 

 marked descending process of the parietal. Fenestra ovalis not sunk 

 in the fundus of a fossa. 



The mandible is remarkable in having but three bones. The articular, 

 angular, and suraugular are coossified, and the spleuial and dentary. 

 The coronoid has little horizontal jiroduction on the outside of the ramus, 

 and the angle of the dentary extends considerably posterior to it. The 

 Meckelian groove is entirely closed. 



The hyoid apparatus is described under the head of the genus 

 XantKsia. 



There is no zygosphen. There are six cervical intercentra besides 

 that of the atlas. The cervical ribs begin on the fourth vertebra. 

 Four of these ribs are of peculiar form, being expanded and truncate 

 at the extremity so as to be somewhat fan-shaped. Neural sj)ines 

 rather low on the cervical and caudal regions, and lower on the dorsal 

 vertebr*. Caudal vertebrte segmented toward the anterior part, the 

 fissure passing through the middle of the diapophyses. Neural spine 

 single, oblique, posterior ; chevron bones normal. 



Suprascapula short and wide ; scapula without proscapula. Coracoid 

 with one notch; sternum without fontanelle. Interclavicle with mod- 

 erate posterior limb. Sternal ribs three; xiphoid rods not juxtaposed, 

 supporting two ribs. No abdominal ribs. 



Pubes meeting at about a right angle; pectineal angles near the 

 middle, decurved. Pubis with tuber exterior. Ilium without augulus 

 cristas; acetabulum entire. 



The teeth have compressed tridentate crowns; those of the premaxil- 

 lary bone are not conic, but have also compressed crowns, where traces 

 of denticles are sometimes apparent. 



The remarkable features in the osteology of this genus are (1) the 

 peculiar relations between the parietal and supraoccipital bones, which 

 resemble the structure seen in a sea turtle; (2) the wide ectopterygoid; 

 (3) the absence of lachrymal ; (4) the presence of only three mandibular 

 elements. The affinities are a mixture of those of the Lacertid:p- and 

 Scincidse; the large postfrontal bones; the descending processes of the 

 parietals, and the form of the pubes, resembling the corresponding parts 

 in the latter family. The expanded cervical ribs resemble those of the 

 Geckonid genus Phyllodactylus. The relations of the parietal and 

 occipital bones are quite different from those found in the Lacertidai 

 and Anguida' {Gerrhonotus, Celestus, Ophisaurus), where the temporal 

 fossa' are also roofed over. In these forms the contact is normal, that 

 is, by the elevated median portion of the anterior border of the occipital. 



Three species of this genus have come under my observation. They 

 may be distinguished by the following characters: 

 fSniall; limbs short, barely overlapping where appressed to the sides. Tail short, 



eijiial from vent to angle of month ; one row of supraocular scales; one parietal 



on each side. Color, light brown with dark brown speckles X. vigilla Baird. 



